2 Answers
2

I see you're writing from India, so the standard US answer of installing light blocking cellular blinds may not apply to you.

Consider using a thin material that reflects light instead of absorbing much of it, such as aluminum foil. If you want it to look nice, you can stack the foil between a light piece of paper for the outside (so the neighbors aren't blinded by the reflection) and cardboard (for rigidity).

The aluminum foil works, I've done it myself, but I like the idea of backing it with cardboard. Maybe making a sandwich out of a few layers of cardboard and foil and then taping it to each individual frame would work. Do you run AC?
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electricsauceJun 24 '11 at 13:42

You want the light for heat in the winter, so I'd take the foil down. Then, block any drafts from the windows. Here, that involves weather stripping and maybe a plastic wrap. If you're improvising, a rolled up towel along the bottom of the window sill is a start.
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BMitch♦Jul 2 '11 at 11:04

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Your English is better than my Hindi. Drafts are gaps that allow cold air to pass. Weather stripping that we get in the US is usually a foam or rubber material that can be compressed in the gap to form an air-tight seal.
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BMitch♦Jul 2 '11 at 15:45

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I did use Aluminium foil in the past summers, and they "did work" superbly. The temperature downfall was remarkably noticeable. Thanks to you.
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abcdDec 6 '12 at 4:13

I'm not sure that this would be available to you locally, but this is what I use on my bedroom. Cuts easy and has a reflective side and is very cheap. Works well enough to keep the Florida heat out of 50 year old leaky windows.